The present invention relates to a thermal transfer recording medium for use with a word processor, printer, facsimile, bar-code printer or the like and, more particularly, to a thermal transfer recording medium which allows a high-precision print image to be transferred onto a paper sheet having a low surface smoothness (hereinafter referred to as "rough paper sheet").
A conventional thermal transfer recording medium allowing for high-quality printing on a rough paper sheet (hereinafter referred to as "thermal transfer recording medium for rough paper") comprises a foundation, a release layer formed on a foundation including a wax as a principal component thereof, and a color ink layer formed on the release layer containing a coloring agent dispersed in a binder with a high melt viscosity including a resin as a principal component thereof.
When an image is printed on a rough paper sheet with such a thermal transfer recording medium, a portion of the color ink layer is transferred onto the rough paper sheet in such a state that the transferred portion bridges troughs of a microscopically undulated surface of the rough paper sheet. However, the high viscosity of the binder leads to less sharp separation of the color ink layer in printing.
To overcome this problem, the addition of fine particles to a color ink layer has been proposed. In a. thermal transfer recording medium including such a color ink layer, the fine particles contained in the color layer exist adjacent to a surface of the color ink layer as shown in FIG. 3 (which is a schematic sectional view of a conventional thermal transfer recording medium), and some of the fine particles partially project from the surface of the color ink layer. When an image is printed on a rough paper sheet with the thermal transfer recording medium, the fine particles partially projecting from the surface of the color ink layer prevent the image from sufficiently adhering onto the rough paper sheet. This results in a failure in image transfer, thereby preventing the printing of a high-precision image.
In view of the foregoing problems, it is an object of the present invention to provide a thermal transfer recording medium which allows for high-quality printing without degrading ink transfer performance to form a high-precision print image even on a rough paper sheet.
The foregoing and other objects of the present invention will be apparent from the following detailed description.